A linearity of a power amplifier is largely affected by an input capacitance of the power amplifier, and a phase of an output signal of the power amplifier may be changed due to the input capacitance when an amplitude of an input signal increases, where this phenomenon is called AM-PM distortion. To make the power amplifier have a stable phase of the output signal, how to design a compensation circuit to improve the linearity of the power amplifier is an importance topic.